This application claims the priority of Korean Patent Application No. 2005-0001336, filed on Jan. 6, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a motor drive control device and, more particularly, to a motor drive control device using a relay switch.
2. Description of Related Art
In general, a motor rotates in the right or reverse direction according to the polarity of voltage applied to the motor. An H-bridge inverter is a circuit configured to switch the polarity of voltage applied from a power supply to the motor. FIG. 1 shows a schematic construction of the H-bridge inverter.
As shown in FIG. 1, a typical H-bridge inverter includes four switching transistors Q1˜Q4 configured in an H-bridge shape with respect to a motor (M). In the H-bridge inverter thus configured, when the switching transistors Q1 and Q4 are turned on, current flows through Q1→motor (M)→Q4, causing the motor to rotate in the right direction. When the switching transistors Q2 and Q3 are turned on, current flows through Q3→motor (M)→Q2, causing the motor to rotate in the reverse direction. In addition, when the switching transistors Q1 and Q3 are turned on, the motor stops operating.
There is a problem in the typical H-bridge inverter in that it is complex to control the motor since four active switches should be controlled to drive the motor. Further, since circuits for using and controlling the four active switches are to be configured, the construction of the entire system becomes complicated and the cost increases.
Alternatively, the H-bridge inverter may be configured using mechanical switches (i.e., relays) to reduce the cost. However, in this case, spark occurs each time the switches are switched on and off, as shown in FIG. 2. This may cause the life of the switch to be reduced and may cause neighboring circuits to be damaged.